Photographic developer



. Patented Apr. 21, 1936 PATENT OFFICE v 2,037,742 rrro'rooaarmc nEvELorER Frits E. Stockelbach, Montclair, N. J. I

No Drawing. Application September 14, 1934,

Serial, No. 744,018

Claims. (01. 95-88) My present invention relates to photographic developers and aims to provide a new class of compounds adapted for such use;

In the developing of images on sensitized pho 5 tographic surfaces which have been exposed to light,it is the general practice to immerse or treat such surfaces with an aqueous, slightly alkaline solution containing an organic reducing agent such as hydroquinone, pyrogallol, mono- 1.0 methyl-p-aminophenol, glycine, etc. Of these developers pyrogallol is one of the oldest and is still considered generally satisfactory; and much used by commercial photographers and by the motion picture industry. Pyr allol, however, 15 has a serious disadvantage in that it is readily oxidizable, and particularly so in alkaline solutions such as used in photographic work. It also has the tendency to impart a yellow tone to the finished negative and a yellow stain to the hands.

The other developers aforementioned are also subject to various drawbacks; for example, some are expensive, others are unstable, and still others require great care in their use because of their toojrapid action, or are inferior or undesirablefor other reasons.

The present invention has for its object to tone to the developed negative and which will be relatively inexpensive.

The class of compounds which possess these characteristics to a marked degree are the alkyl substituted pyro-gallols, for example, the mono and the di-alkyl substituted pyrogallols such as mono ethyl pyrogallol, di-ethyl pyrogallol and mono tertiary butyl pyrogallol. The normal mono propyl pyrogallol also possesses certain of these characteristics to a markedldegree butis not as soluble as the other alkyl substituted pyrogallols enumerated. All of these alkyl substituted pyrogallols are powerful reducing agents in both neutral and alkaline solution, do not tend to stain the hands or the negativeyellow, and at temper:

in alkaline solution.

A typical example of a developer using any of this (Sass of alkyl derivatives of pyrogallol may beprovlded'as follows:

atures of -90F. are comparatively stable even a Two solutions, A and B, are first prepared:

. Solution .4

Sodium bisulphite- 50 grams Alkyl substituted pyrogallol 87.5 grams 5 Potassium bromide 1.6 grams Distilled water 2100 cc.

Solution 3 Anhydrous sodium carbonate; grams 10 Anhydrous sodium sulphite 153 grams Distilled water 2100 cc.

cc. of solution A is added to 700 cc. of distilled water and 150 cc. of solution B is then mixed 15 therewith. Using this resulting solution I have found that a correctly exposed plate or film develops completely at a temperature of 75-85 F.

- within four or five minutes. To fix this developed plate or film it should be rinsed for thirty 20 or forty seconds in distilled water acidified with a little glacial acetic acid,, and thereafter treated in an acid fixing bath, after which the plate or film is washed in water to remove the adherent fixing salt.

Mono and di-ethyl pyrogallol are described in chemical literature and their method of preparation will not here be given. Mono tertiary butyl pyrogallol, as far as I am aware, is mentioned nowhere in chemical literature, and to 30' the best or my knowledge and belief is a new compound. It may be prepared by condensing pyrogallol with tertiary butyl alcohol, using one of the usual condensing agents such as zinc chloride. After the condensation iscompleted the 3 reaction product is shaken out with a solvent 1 such as toluoi, allowed to crystallize, and finally purified by distillation under high vacuum and crystallization from water. When crystallized from water it forms white crystals having a melting point of 138-139.2 C: which are readily soluble in water and organic solvents.

When a drop of dilute ferric chloride is added to an aqueous solution of mono tertiary butyl 4 I pyrogallol it produces a light purple color which quickly disappears. If, following this, a drop of a dilute solution ofsodium carbonate is added, a deep violet color is produced. A silver nitrate solution is reduced instantaneously by adding a 50 few drops of the aqueous solution of mono tertiary butyl pyrogallol thereto.

Specifically, mono tertiary butyl pyrogallol may be prepared as follows:

In a flask provided with an agitator there are 55 subsided the mixture is heated to 120 C.

by considerable foaming,. at which point exterior cooling may be necessary After thereaction has and maintained there for about an hour. The product is then cooled to room temperature, 300 c. c.

distilled water added thereto and the butyl pyrogallol extracted with ether.

The ether extract is washed twice with 300 c. c. of water containing a few drops of hydrochloric acidand the ether is finally distilled off, the last traces thereof. being removed under vacuum. The crude butyl pyrogallol is then purified by distillation under vacuum and boils at 165-1'70 C. at 2 to 3 mm.-pressure.- The yield of distilled mono tertiary butyl pyrogallol will be approximately 500 grams. This distilled product may be further purified by crystallization from water-in which when hot it is readily soluble, but when cold, only soluble to the extent of from 3% Normal mono propyl pyrogallol is most readily prepared from the corresponding ketone 4-propionyl pyrogallol by-reduction according to Clemmensen. When purified and crystallized, it forms crystals with a melting point -108110 C. which are rather difiicultly soluble in water but fairl soluble in organic solvents.

Although I have set forth but a few of the compounds of the general class to which my invention is applicable, and have given but a single type formula for a devolping solution, it is of course understood that the invention is not to be construed as limited by. any of the examples given 5. A photographic developer comprising a solution of a mono ethyl substituted pyrogallol.

6. A photographic developer comprising a solution of a di-ethyl substituted pyrogallol.

photographic surfaces which have been exposed to light, which comprises subjecting said surfaces to the action of a solution containing an alkyl substituted pyrogallol.

'12. A process of developing images on sensitized photographic surfaces which have been exposed to light, which comprises subjecting said surfaces to the action of a solution containing a mono ethyl pyrogallol.

13. A process of developing images on sensitized photographic surfaces which. have been exposed to light, which comprises subjecting said surfaces to the action of a solution containing a di-ethyl pyrogallol.

14. A process of developing images on sensitized photographic surfaces which have been exposed to l ght, which comprises subjecting said surfaces to the actionof a solution containing a mono tertiary butyl pyrogallol.

15. A process of developing images on sensitized photographic surfaces which have been exposed to light, which comprises subjecting said surfaces to the action of an alkaline aqueous solution containing an alkyl substituted pyrogallol.

F'RITS E. STOCKELBACH. 

